As a catalyst used widely in such important fields as fuel cell, electrosynthesis, etc., platinum (Pt) has attracted interest for a long time. Nanonization of Pt catalysts is a major direction of research, and has been under intensive study in the past twenty years. However, just like other catalysts, particles resulting from nanonization suffer from many problems such as coagulation, poor stability, etc. A key point to develop this series of catalysts is further enhancement of the performance, utilization efficiency and service life of Pt catalysts.
Tungsten carbide (WC) is a non-noble metal catalytic material having good performance, and its potential use as a catalyst has been paid close attention to since it was reported to have good catalytic activity for dehydrogenation of cyclohexane and dehydrogenation of ethyl benzene to styrene in 1960s. It was reported by literature (see literature: Science, 1973, 181: 547) that the surface electron layer of WC was similar to that of Pt, and showed catalytic activity similar to that of Pt in some reactions. WC has not only characteristics that enable it to replace noble metal catalysts such as Pt, etc. and good anti-poisoning ability, but also strong acid resistance and good electrocatalytic activity. However, due to the high temperature steps in preparation of WC and its relatively high specific gravity, its increase of specific surface area is limited, and thus increase of porosity and inhibition of particle coagulation are the main feasible directions of research (see literature: Microporous and Mesoporous Materials 2012, 149: 76). Hence, preparation of a WC-Pt composite material with well-dispersed tungsten carbide having mesoporous structure as the main component of the catalyst can not only reduce the amount of Pt used and thus lower the cost of the catalyst, but also increase the stability of the composite material and prolong the service life. Further, since carbon nanotube (CNT) has long been regarded as a good material for matrix, and has excellent mechanical, electronic, thermodynamic and other characteristics, its incorporation into a composite sample can increase porosity, specific surface area, electric conductivity and inhibit particle coagulation effectively. Existing Pt/WC, Pt/CNT, WC/CNT catalysts are mainly supported catalysts, and the preparation of the composite materials is fulfilled by supporting binary component particles on a matrix(WC, CNT, or WC/CNT). Moreover, the support of Pt is mostly accomplished by gas phase reduction or chemical reduction, wherein the process is relatively complex, causing difficulty in control over cost and process standardization, such that large scale preparation is difficult. Therefore, in order to improve the catalytic activity and stability of nano Pt remarkably, the key and critical approach is preparation under controllable conditions of a composite catalyst characterized by good Pt dispersity and developed porosity of WC or CNT matrix. Furthermore, if some components can be prepared concurrently to reduce preparation steps, production time, energy consumption and production cost originating therefrom may be further reduced greatly.
Up to now, there has never been any report on the preparation of spherical WC/CNT/Pt composite material and WC/CNT composite material by simultaneous process.